SQL Server NULLIF() Function

The NULLIF() function in SQL Server compares two expressions. If they are equal, it returns NULL; otherwise, it returns the first expression.

NULLIF(): Definition and Usage

NULLIF() is handy for situations where you want to treat equality between two expressions as a special case, resulting in a NULL value. This can be very useful in various data manipulation tasks and conditional logic within your SQL queries. It's a concise way to handle cases where you want to treat equality as a specific condition resulting in a null value.

Syntax

NULLIF(expr1, expr2)
      

Parameter Values

Examples

Comparing Identical Numeric Values

This example shows that when both expressions are equal, NULLIF() returns NULL.

SELECT NULLIF(25, 25);
      

NULL
      

Comparing Identical String Values

Similar to the above, but with strings.

SELECT NULLIF('Hello', 'Hello');
      

NULL
      

Comparing Different Values

When the expressions are different, the first expression is returned.

SELECT NULLIF('Hello', 'world');
      

Hello
      

Comparing Identical Date Strings

Demonstrates the behavior with date strings.

SELECT NULLIF('2017-08-25', '2017-08-25');
      

NULL